The invention relates to a rotary-latch lock which comprises a forked rotary latch that is blocked against pivoting in a position where it locks a closing bolt through a spring-loaded catch member which has a detent edge that engages behind a centrally directed catch edge extending from a circumferential edge of the forked rotary latch.
Rotary-latch locks of this general type are already known from German Auslegeschrift No. 2,018,197 and are in widespread use as door locks of motor vehicles.
However, rotary-latch locks, in addition to their use in or on vehicles, can also be employed for other locking functions where high locking safety is required.
Nevertheless, the high locking safety of a rotary-latch lock can be impaired if exposed to high dynamic loads which lead to rotational oscillations of the forked rotary latch.
In motor-vehicle door locks, such rotational oscillations are brought about by relative movements which occur between the closing bolt and the forked rotary latch engaging around it and which are attributable to body distortions or the like.
Because of rotational oscillations of the forked rotary latch, the detent pawl can be vibrated which can result in a movement of the detent pawl counter to its spring-loading direction. Under extreme circumstances, this can lead to "creeping movement" along the catch edge of the forked rotary latch that can cause complete disengagement of the detent pawl, after which the likewise spring-loaded motor vehicles forked rotary latch snaps into its opening position. In motor vehicles especially, an unintentional release of the lock must be prevented for safety reasons.
To guarantee against unintentional release of a rotary-latch lock, the locking contour of conventional rotary-latch locks is equipped with an "undercut", that is to say the detent pawl and the catch edge of the forked rotary latch are so coordinated with one another that the operation of disengaging the detent pawl is necessarily associated with a greater or lesser angular rotation of the forked rotary latch in the closing direction. The larger the "undercut", the higher the safety of the rotary-latch lock against unintentional release.
However, in the inherently effective principle of an `undercut` of the locking contour, it is necessary to allow for the fact that, with an increasing "undercut", the unlocking forces also increase. Excessively high unlocking forces are likewise undesirable, because they have an adverse affect on the ease with which the rotary-latch lock is operated in order to release it.
An object of this invention is to therefore improve a rotary-latch lock of the relevant generic type, to the effect that, when used for locking functions on constructional parts subjected to oscillatory load, it can offer a high degree of locking safety without any effects on the unlocking forces.
A solution for improving such a rotary-latch consists of having the catch edge be a limiting edge of an approximately U-shaped catch recess of the forked rotary latch and into which a detent end of the catch member engages in the locking state. A rear edge of the detent end is located opposite a limiting edge of the catch recess at a distance which, in the event of oscillating movements of the forked rotary latch, allows the limiting edge to butt against the rear edge of the detent end of the spring loaded catch member. The limiting edge and the corresponding rear edge are designed over their length of mutual contact as return surfaces, which during the time when they butt against one another, cause an acceleration force acting in the direction of engagement to be transmitted to the detent end. Surface normals of the return surfaces form an acute angle with an engagement line determined by the direction of advance of the detent end. The return surface of the catch member is a straight edge on the detent end and the return surface of the rotary latch is a straight limiting edge of the catch recess. Shock pulses of the return surfaces butting against one another, with the catch member partially disengaged, ensure that the catch member is returned in the direction of engagement of the catch member and the rotary latch.
An advantageous embodiment of the invention is obtained by having an engagement line of the detent end of the catch member intersect the circular area covered by the forked rotary latch and at a distance from the pivot axis of the rotary latch. The return surface is arranged radially with respect to the pivot axis of the rotary latch.
The catch member is a pivotably mounted detent pawl. The surface normals of the return surfaces of the rotary latch and the detent pawl extend respectively at a distance from the pivot axes of the forked rotary latch and the detent pawl.
The detent end projects transversely relative to the main longitudinal extension of the detent pawl.
It is also advantageous if a transitional region between the return surface of the detent end and a fore-edge of the detent end is arcuately curved.
The limiting edge of the catch recess (equipped with the return surface) is set back from the catch edge as seen in the direction of advance of the detent end.
The detent end widens in a wedge-shaped manner in the direction of its fore-edge between the detent edge and the return surface of its rear edge.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.